Problem: Luis ate 2 slices of pizza. Tiffany ate 2 slices. If there were initially 9 slices, what fraction of the pizza was eaten?
Explanation: $\text{fraction of pizza eaten} = \dfrac{\text{number of slices eaten}}{\text{number of slices total}}$ They ate ${4}$ out of $9$ slices. They ate $\dfrac{4}{9}$ of the pizza.